docs: def delta_cdf(self, d_min, d_max, n=None):
          r'''Computes the difference in cumulative distribution function between
          two particle size diameters.
                      
          .. math::
              \Delta Q_n = Q_n(d_{max}) - Q_n(d_{min}) 
                      
          Parameters
          ----------
          d_min : float
              Lower particle size diameter, [m]
          d_max : float
              Upper particle size diameter, [m]
          n : int, optional
              None (for the `order` specified when the distribution was created),
              0 (number), 1 (length), 2 (area), 3 (volume/mass),
              or any integer, [-]
  
          Returns
          -------
          delta_cdf : float
              The difference in the cumulative distribution function for the two
              diameters specified, [-]
          
          Examples
          --------
          >>> psd = PSDLognormal(s=0.5, d_characteristic=5E-6, order=3)
          >>> psd.delta_cdf(1e-6, 1e-5)
          0.9165280099853876
          '''
          return self.cdf(d_max, n=n) - self.cdf(d_min, n=n)